For quite some time, I was puzzled why my CDI660 was stuck in a reset loop after I inserted the test/dummy plug into Input 1. I expected it to boot into the Service Shell, like most other CD-i players. My solution so far was to use a 490 system ROM in the 660 whenever I needed the Service Shell (the compatibility and also the error were discovered during this experiment). However, this wasn’t a very practical approach because I had to open up the player and dig out the system ROM from underneath the DVC every time.

When CD-i Emulator with -testplug option showed the same behaviour, CD-i Fan figured out what is causing this error: The Service Shell module sv is missing from the 660/670 system ROM.
In this article, I will show you a simple ROM patch to enable the Service Shell for the CDI660.